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ComputerAided_Design_Engineering_amp_Manufactur.pdf

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from the FBDS. The user also specifies various technological information attributes such as surface finish<br />

and hardness specifications of the part in addition to the task of creating the part geometry. The technological<br />

information attributes are written to an output file while the geometric information of the part is written<br />

to a universal file formatted CAD output file. 18 The CAD output file is interpreted by an interface program<br />

and all relevant geometric and technological information associated with the features is translated to the<br />

product data model of the part. The process planner interprets the PDM and develops the process plans<br />

for the part. The process plan is then written in a suitable format for use in manufacturing. Subsequently,<br />

the process plan information is used for generating the NC tool path for machining the features on an NC<br />

machine tool, utilizing the services of a dedicated NC tool path planning module.<br />

Blackboard-Based Process Planner<br />

The blackboard (BB) architecture-based process planning framework has been implemented in a prototype<br />

expert system BBPP, using the CLIPS expert system shell. (The current capabilities of the BBPP<br />

system are summarized in Table 1.3.)<br />

The domain expertise of the various participating experts (knowledge sources in BB terminology) that<br />

have been incorporated in the BBPP system is shown in Table 1.4. The control expert (control component<br />

in BB terminology) consists of a set of rules that performs the following functions (Figure 1.9): (a)<br />

correlating and interpreting data provided by different experts, (b) directing the solution generation<br />

process between two subsequent process planning phases, (c) activating the participating experts on the<br />

basis of the current state of the BB data base, and (d) directing output from the BB in each one of the<br />

process planning phases to the appropriate sections of the route sheet. The rules for the control expert<br />

have been developed on the basis of some heuristic control algorithms. In the BBPP system, the process<br />

planning task is partitioned into five separate phases that correspond to certain activities being performed<br />

during process planning.<br />

The BB data base is a data structure in which slots are provided for the specification, retrieval, and<br />

modification of different types of data pertaining to the different segments of the process plan (Table 1.5).<br />

The different participating experts refer to the BB data base for the data required to perform their tasks<br />

© 2001 by CRC Press LLC<br />

TABLE 1.3<br />

Current Capabilities of BBPP System<br />

Process Plan Feature Capability<br />

<strong>Manufactur</strong>ing features Slots, Pockets, Protrusions, and Holes<br />

Machining process Drilling, Boring, Shaping, Planning, Slab Milling, End<br />

Milling, and Sawing<br />

Finishing operations Reaming and Grinding<br />

Heat treatment operations Quenching, Carbonitriding, Cyaniding, and Carburizing<br />

TABLE 1.4 Domain Expertise of Different Experts in the<br />

BBPP System<br />

Name of Expert<br />

Fields of Expertise in the<br />

Process Plan Domain<br />

Machining Machining strategies<br />

Machine-tools Machine-tool capabilities<br />

Cutting-tools Cutting-tool information<br />

Material Material behavior<br />

Cost Machining and manufacturing cost<br />

Surface finish Finishing operations<br />

Heat treatment Heat treatment operations<br />

Machinability Machining parameters<br />

Setup Machining setups<br />

Sequence planning Setup sequencing

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